The CAS Registry Mumber 7750-30-3 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,7,5 and 0 respectively; the second part has 2 digits, 3 and 0 respectively. Calculate Digit Verification of CAS Registry Number 7750-30: (6*7)+(5*7)+(4*5)+(3*0)+(2*3)+(1*0)=103 103 % 10 = 3 So 7750-30-3 is a valid CAS Registry Number.